1. Field of the Invention
The present invention relates to an organic glass for automobile and a process for producing the organic glass for automobile, and in particular to an organic glass for automobile that is favorably used as a front glass, a rear glass, a window glass, and the like for automobile, and to a process for advantageously producing the organic glass for automobile.
2. Discussion of Related Art
In recent years, weight reduction of automobile is promoted to protect the environment and to improve fuel efficiency. As one way of reducing the weight, the use of the organic glass in an automobile has been studied. As a material of the organic glass (resin glass) for automobile, various resin materials that are able to form a transparent flat plate can be employed. Examples of the resin materials include polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, and ABS. Among these resin materials, polycarbonate is favorably employed, because it is excellent in impact-resistance, heat-resistance, and transparency. However, the organic glass has lower surface hardness than the inorganic glass, no matter what kind of resin is used to form the organic glass. Thus, wear-resistance and abrasion-resistance of the organic glass is insufficient, and also weatherability is poor.
To solve the above problem, JP-A-9-239937 and JP-A-11-227092, for example, propose an organic glass which includes a hard coat layer obtained by applying an organic coating material such as a silicon coating material on a surface of a transparent resin base plate formed of polycarbonate. Further, JP-A-2-66172, JP-A-2004-237513, and JP-A-2004-175904 propose an organic glass that includes a hard coat layer having a multilayer structure, which is formed on a surface of a transparent resin base plate made of polycarbonate. The multilayer structure consists of a coating film, which is formed of an organic coating material such as a silicon coating material or an acrylic coating material, and a thin film of silicon oxide (SiO2), which is formed on the coating film by a vacuum deposition process such as plasma CVD, sputtering, and electron beam deposition.
When the organic glass includes a hard coat layer containing a coating film formed of an organic coating material that is positioned on a surface of the resin base plate, the weatherability can be improved by the presence of the coating film formed of the organic coating material. Further, the organic glass can have better weatherability by adding an ultraviolet (UV) absorber or infrared (IR) absorber, for example, into the organic coating material. The organic glass that contains a hard coat layer having a multilayer structure consisting of a coating film formed of an organic coating material and a thin film of silicon oxide can have a surface hardness that is equivalent to an inorganic glass by the presence of the thin film of silicon oxide, thereby, stably securing sufficient wear-resistance and abrasion-resistance.
However, the above conventional organic glass involves the following problems. When the conventional organic glass is produced, a coating operation is performed to form the hard coat layer including the organic coating film. The coating operation is a wet type process, and thus a drying process is required. In addition, when the organic coating film has a multilayer structure, the drying process should be repeated. Further, the resin base plate formed of polycarbonate, for example, has poor adhesion to the organic coating material. Therefore, when the hard coat layer including the organic coating film is formed on a surface of the resin base plate, a primer layer should be formed between the resin base plate and the hard coat layer to improve the adhesion thereof.
Thus, the conventional organic glass requires an operation that involves a lot of time and labor in order to form the hard coat layer including the organic coating film. Further, as equipments for forming an organic coating film, the conventional organic glass requires equipment for purifying the space for coating operation in order to prevent a foreign substance from being mixed into the coating film, in addition to the coating equipment for organic coating material and the drying equipment. Therefore, cost of equipments is inevitably increased.
In the formation of the hard coat layer including the organic coating film, when the organic coating material into which a large amount of an ultraviolet absorber or an infrared absorber is added is used, problems such as reduction in pot life of the coating material and deterioration of leveling properties due to the increased viscosity may be arisen. Therefore, there is a limit to the improvement in the weatherability of the conventional organic glass that is obtained by the addition of the ultraviolet absorber or infrared absorber into the organic coating material.
Further, the organic glass containing the hard coat layer having the multilayer structure consisting of the organic coating film and the inorganic coating film formed by a vacuum deposition process requires both of the dry coating process and the wet vacuum deposition process in the production thereof. Therefore, a large-scale equipment is needed and the cost thereof is inevitably high.